If you thought the biggest problem facing the sea was plastic, overfishing, or that unfortunate encounter with a sea urchin, think again. This Monday at the Faculty of Chemistry and Technology in Split, we learned something you won’t find in tourist brochures: the sea is becoming more acidic.
No, no one accidentally poured vinegar into it. This is a serious process called ocean acidification, which occurs because the oceans absorb increasing amounts of carbon dioxide (CO₂) from the atmosphere. The result? A drop in pH levels that slowly but surely disrupts the entire marine world, from shellfish and plankton to corals and fish. Sounds like another boring chemistry lesson? In a short time, through her lecture “Ocean acidification: causes and consequences,” Assoc. Prof. Maša Buljac shattered all our seaside illusions and rocked the boat of ecological reality along the way. But don’t panic, all is not lost. Let’s take it step by step!
The lecture was organized as part of the project Let’s Sail into STEM Waters – A Ticket to 2030, run by the Sunce Association.
What is ocean acidification, and why should we care?
Humans love releasing CO₂ into the atmosphere (through breathing, driving, industry, heating, and more), and the oceans have silently absorbed it until now. But they can no longer keep up with the pace. Carbon dioxide dissolves in seawater and forms something every chemist knows well: carbonic acid. This acid lowers the pH of the ocean and… voilà! Acidified seas.
No, it won’t corrode your feet when you step into the shallows but it will slowly corrode the entire marine ecosystem.
Assoc. Prof. Buljac explained how acidified seawater literally prevents some organisms from developing normally. Take shellfish, for example. They need calcium carbonate to build their shells.
Forgive us for a bit of chemistry. In more acidic seawater, excess hydrogen ions (H⁺) bind to carbonate ions (CO₃²⁻) and convert them into bicarbonate (HCO₃⁻). This reduces the amount of free carbonate available to shellfish. And without cooperation between carbonate and calcium, there’s no shell. Imagine trying to build something out of LEGO while someone keeps taking away your pieces. That’s what shellfish are facing today.
Plankton, the foundation of the marine food chain, face the same problem. Their delicate shells can even begin to dissolve, as if exposed to a mild acid. And without plankton, there’s no food for small fish. And without small fish… well, we’re no longer part of the story either.
Fish in their larval stage are particularly vulnerable, they’re like marine babies, and babies, as we know, are highly sensitive. Acidified water can disrupt their development, orientation, and even their sense of smell (which fish, believe it or not, rely on heavily).
Corals are like the architects of underwater cities just without the degrees. But acidified water prevents them from building. Instead of growing, corals give up. Under stress, they lose their color through a process called bleaching. And once they turn white, there’s no going back. They die.
Along with them disappear thousands of species that live on coral reefs. That’s not just sad it’s ecological chaos.
Can we do anything besides despairing by the sea and counting dying shellfish?
If we continue on this path, scientists’ predictions are far from optimistic. By the end of the century, ocean pH could drop by an additional 0.3 to 0.4 units. It may sound small, but in chemical terms, it represents a drastic change. This could cause mass coral die-offs, declines in shellfish and plankton populations, and disruptions across entire marine food webs. Ultimately, that means fewer fish, less food, threatened fisheries and tourism, and a major blow to biodiversity all due to an invisible yet pervasive change in ocean chemistry.
The good news is that we are not completely powerless. Assoc. Prof. Buljac mentioned the Paris Agreement, a global commitment to reducing greenhouse gas emissions. It’s like the whole world finally deciding to turn down the thermostat on Earth and slow down global warming.
But beyond major political agreements, there is much we can do as individuals. Here are a few suggestions from the lecture (and from life in general): cycle more, drive less, reduce plastic use, recycle more, get involved in local environmental activities, and spread knowledge because you never know who might listen.
In conclusion, what have we learned?
The sea is adaptable, but it has limits. It has been absorbing our mistakes for decades, but now it is sending a message: “Hey humans, enough is enough!” Ocean acidification is not a theory it is a reality. And we can choose whether to be part of the problem or part of the solution. This lecture opened our eyes and showed us that even “invisible problems” like ocean acidity can turn into visible catastrophes if we ignore them.
We didn’t wear diving gear, but we dove deep into an issue that concerns us all. And now that we know what’s happening beneath the surface, we have no excuse to stay dry.
The project Let’s Sail into STEM Waters – A Ticket to 2030 does not aim only to popularize science; it seeks to bring STEM closer to everyone from teachers to volunteers, from students to activists. Because science does not live only in laboratories, it lives in every glass of water, every piece of waste, and every decision we make.
The project is led by the Sunce Association for Nature, Environment and Sustainable Development (Split). Partners include the “Krka” Ecological Association (Knin), the Faculty of Chemistry and Technology, the Faculty of Humanities and Social Sciences, the Association of Chemical Engineers and Technologists Split, and two primary schools—Domovinske zahvalnosti and DOBRI.
The project is funded by the European Union through the European Social Fund Plus (ESF+) under the Effective Human Resources 2021–2027 program and co-financed by the Office for NGOs of the Government of the Republic of Croatia.
The views expressed in this article are the sole responsibility of the author and do not necessarily reflect the views of the European Union or the Office for NGOs of the Government of the Republic of Croatia.